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Performance enhancement of a Latent Heat Thermal Energy Storage for Domestic Hot Water production
No full textInternational audienceThis study numerically investigates different ways to enhance the discharge performance of a Latent Heat Thermal Energy Storage for Domestic Hot Water production, from a design point of view. The storage design is based on the tube-and-shell heat exchanger concept. The tube bundle comprises 37 tubes arranged with a hexagonal pattern, and carrying radial fins to boost PCM conductivity. A dynamic model of the storage, built on Dymola platform, is used to assess the impacts of the Phase Change Material and the hydraulic path on the useful capacity of the storage and its discharge efficiency. We show that using RT 70 HC (melting temperature 70°C) instead of octadecanol (melting temperature 58°C) permits to increase storage useful capacity by 38%. We also show that useful capacity is further increased by 14% if Heat Transfer Fluid flow is arranged in 3 passes instead of 1. The study concludes that, by integrating all these features into an optimal design, it is possible to boost storage performance for Domestic Hot Water production
Deciphering the nature of secondary Ag S species in soils polluted with Ag nanoparticles
No full textInternational audienceSilver nanoparticles Soil X-ray absorption near edge structure (XANES) spectroscopy Nano X-ray fluorescence (nXRF) A B S T R A C T Ag₂S nanoparticles (Ag₂S-NPs) are the main silver species in sewage sludge and soils polluted with silver nanoparticles (AgNPs). Uncertainties about Ag + release and nano-Ag₂S toxicity prompted us to further investigate Ag speciation and distribution under realistic conditions. In a previous study we found by bulk X-ray absorption spectroscopy (XAS) that besides Ag 2 S, a secondary Ag -S species was present in sewage sludge and soils. This species accounted for 24-36 % of total silver. The objective of the present work was to investigate the nature of this Ag-S species. A combination of X-ray absorption near edge structure (XANES) spectroscopy at Ag K and L III edges at micro and nano resolutions and of S K-edge micro XANES were used. Nano X-ray Fluorescence (nXRF) was used to investigate the nanoparticle size distribution and to evaluate the presence of mixed metal sulfides. We identified the secondary Ag-S species as Ag bound to thiol groups of organic matter (Ag-thiolate). It was present around the Ag 2 S-NPs, and likely resulted from the complexation of Ag + by thiol groups of soil organic matter. Ag 2 S-NPs displayed a variety of sizes, with 10 % to 40 % of particles bellow 100 nm. Mixed metal sulfides were also present. This study improves our understanding of the fate of Ag-NPs in terrestrial environments, highlights the potential reactivity of Ag 2 S-NPs in soils, and shows the primary role of soil organic matter as a sink for released Ag + . This multi-scale, high-resolution approach represents a novel and powerful methodology for studying nanoparticle behavior in complex environmental matrices
Development and multiscale characterization of sensible/sorption bimodal heat storage for cooling tower applications
No full textAnalyse 3D multi-scalaire de la grotte de la Tête du Lion (Ardèche, France)
No full textThe Lion's Head Cave was discovered in 1963 and quickly classified. Excavations (1972-1973) intersected archaeological levels dated to the upper Paleozoic period and a clearing allowed a clastic filling to be crossed. Paleolithic access is an open question between an option from the slope and another from the source of the filling. 3D surveys were carried out on the site at several scales: (i) large with long-range scanner surveys on the rocky escarpment and photogrammetric processing of old aerial photos, (ii) median with short-range surveys, in the cave, on the road and in the rock shelters and (iii) fine with a photogrammetric survey of the decorated panel. This 3D production is grouped into a single multi-scalar and multi-resolution model, supporting different analyses.La grotte de la Tête du Lion est découverte en 1963 et rapidement classée. Des fouilles (1972 -1973) ont recoupé des niveaux archéologiques datés paléo sup. et une désobstruction a permis de franchir un remplissage clastique. L'accès paléolithique est une question en suspens entre une option depuis le versant et une autre depuis la source du remplissage. Des relevés 3D ont été effectués sur le site à plusieurs échelles : (i) large avec des relevés scanners longue portée sur l'escarpement rocheux et un traitement photogrammétrique de photos aériennes anciennes, (ii) médiane avec des relevés courte portée, dans la grotte, sur la route et dans les abris sous roche et (iii) fine avec un relevé photogrammétrique du panneau orné. Cette production 3D est regroupée dans un unique modèle multi-scalaire et multi-résolution, support à différentes analyses
Enjeux de légitimité dans la médiation scientifique: approche par les usages du livre
No full textInternational audienceCet article porte sur le statut du livre à la fois dans sa dimension symbolique et fonctionnelle afin d’interroger les évolutions de la médiation scientifique et les tensions entre différentes représentations de la science et du public, dans un univers où se croise une grande diversité d’acteurs. L’hypothèse est que pour répondre à leur objectif de reconnaissance, les acteurs de la médiation scientifique ont recours à différents éléments symboliques, dont le livre en tant que représentant d’une connaissance scientifique fiable et stabilisée. Objet-frontière, le livre permet d’articuler différents métiers et compétences de la médiation scientifique. Indirectement, il sert à asseoir la légitimité des discours et des acteurs, ainsi qu’à ouvrir sur des dispositifs dans lesquels la place du public est reconsidérée
Caractérisation mécanique du contrôle postural de la personne en position debout
No full textThe study of postural control is of great interest to researchers from various fields, including robotics for prosthesis design and the medical sector to prevent falls. Despite this, the understanding of the dynamic mechanisms of bodily coordination in an orthostatic posture remains incomplete.With the goal of improving our knowledge of postural control, we approach the mechanical characterization of postural control in a standing position. A mechanical model is chosen to describe this control, in which the human body is represented as a system described by two models: one structural and the other behavioral.The structural model relies on representing the body as a single segment, similar to an inverted pendulum, where the center of gravity slightly projects forward of the ankle's axis of rotation. This modeling involves determining the position of the ankle's axis of rotation and the center of mass, determined from the position of the center of pressure.In the behavioral model, the inverted pendulum is passively stabilized a priori by a spring, simulating the action of the muscles and tendons of the lower limb, thus allowing the body to stand while minimizing muscular effort.An experimental method, including the use of force platforms and the participation of human subjects, is implemented to validate these structural and behavioral models. The experimental results, obtained in different standing situations, show that, in an orthostatic posture, each subject is slightly tilted forward and controls their posture through forward and backward movements with the minimum possible effort (confirmed by the measurement of tangential forces).Through this mechanical analysis framework, the results of this thesis enhance the understanding of postural control in a standing position. Beyond understanding, particularly in the context of fall prevention, if these mechanisms can be deciphered, it paves the way for the development of more efficient and energy-saving humanoid robots, compared to current models on the market, which are often energy-hungry.L'étude du contrôle postural intéresse vivement les chercheurs de divers domaines, notamment la robotique, pour la conception de prothèses, et le secteur médical, afin de prévenir les chutes. Malgré cela, la compréhension des mécanismes dynamiques de la coordination corporelle en posture orthostatique reste encore partielle.Avec la perspective d'améliorer notre connaissance autour du contrôle postural, nous abordons la caractérisation mécanique du contrôle postural en position debout. Un modèle mécanique est retenu pour décrire ce contrôle, dans lequel le corps humain est représenté comme un système décrit par deux modèles : l'un structurel et l'autre comportemental.Le modèle structurel repose sur la représentation du corps sous la forme d'un seul segment, similaire à un pendule inversé, où le centre de gravité se projette légèrement en avant de l'axe de rotation de la cheville. Cette modélisation implique la détermination de la position de l'axe de rotation de la cheville et du centre de masse, déterminée à partir de la position du centre de pression.Dans le modèle comportemental, le pendule inversé est stabilisé a priori de façon passive par un ressort, simulant l'action des muscles et des tendons du membre inférieur, permettant ainsi au corps de se tenir debout tout en minimisant les efforts musculaires.Une méthode expérimentale, incluant l'utilisation de plateformes de force et la participation de sujets humains, est mise en place pour valider ces modèles structurels et comportementaux. Les résultats expérimentaux, obtenus dans différentes situations de position debout, montrent alors que, dans une posture orthostatique, chaque sujet est légèrement incliné vers l'avant et contrôle sa posture par des mouvements d'avant en arrière avec le minimum d'effort possible (confirmé par la mesure des efforts tangentiels).Grâce à ce cadre d'analyse mécanique, les résultats de cette thèse enrichissent la compréhension du contrôle postural en position debout. Au-delà de la compréhension, notamment dans le cadre de la prévention des chutes, si ces mécanismes peuvent être décryptés, cela ouvre la voie au développement de robots humanoïdes plus efficaces et économes en énergie, en comparaison avec les modèles actuellement sur le marché, qui sont souvent énergivores
Deep time evolution of the Latitudinal Diversity Gradient: Insights from mechanistic models
No full textInternational audienceThe latitudinal diversity gradient (LDG) designates the increase in species richness toward the tropics. While geological and climatic changes are recognized as key drivers, the precise factors and their relative contributions to species richness gradients remain debated. Using a spatially explicit eco-evolutionary model, we simulate diversification over 125 million years. We validate the model with empirical mammalian richness patterns, and uncover a pivotal role of paleoclimate and paleogeography. This approach allows us to investigate both the mechanisms driving the LDG and space and time variations in species diversification rates across dynamic landscapes integrating changes in tectonic, climatic and surface processes. We show how scale-dependent surface processes are a key driver of regional diversity patterns and how LDG can emerge under a wide range of eco-evolutionary scenarios. Plate tectonics and the subsequent enduring uneven distribution of land masses within the North and South hemispheres imprinted an asymmetric pattern of species diversification rates, primarily shaped by paleoclimate and paleogeography and only to a lesser extent by surface processes. Our simulations also indicate that the LDG has persisted since the Cretaceous, steepened and stabilized from the early Cenozoic on. The modeled scenarios depict that species primarily originate in the tropics and disperse toward the poles without losing their tropical presence. The tropics not only served as a cradle, fostering the origination of new species, but also as a museum, preserving biodiversity over deep time
Overview of research on NH3-H2O absorption heat pump and refrigeration cycles including generator/absorber heat-exchangers
No full textInternational audienceIn studies to improve the efficiency of absorption machines, the generator/absorber heat-exchange (GAX) cycle is one of the main ways of using internal heat recovery without over-complicating the system. In this paper, the different architectures of the GAX cycle studied from 1986 to 2023 have been synthesized and analyzed. The standard GAX cycle (SGAX) is the most studied. In addition, by adding a pump or a compressor, branched GAX (BGAX) and hybrid GAX (HGAX) cycles have also been studied with a Coefficient of Performance (COP) improvements by up to 30%. In addition, the overview provides details of assumptions in the numerical studies used to simulate operation of the GAX cycle. Experimental results obtained from the literature prototypes are also introduced. A new method to compare the COP obtained in different studies, which depends on the Driving Force (DF) and the Gross Temperature Lift (GTL) is presented. This method is easy to be implemented, giving a rapid interpretation of the results. Experimental results show that in the chiller mode when DF is 100 ℃ and GTL decreases from 40 to 25 ℃, COP increases from 0.39 to 0.54. Meanwhile, in the heat pump mode when DF increases from 125 to 140 ℃ and DF decreases from 50 to 35 ℃, COP increases from 1.60 to 1.73
Hand-operated fully reproducible static blade core opening bench
No full textInternational audienceThe EDYTEM Manual Core Opening Bench (MCOB) is a manually operated tool designed for opening soft sediment cores. This reproducible device was inspired by several existing, but as yet unpublished, models and was developed to ensure clean and precise cuts without contamination from plastic debris. The system comprises six technical components (frame, guiding system, sled, drive mechanism, core holding system, and cutting tools) and can accommodate cores of various diameters. Its hand-operated design enhances both safety and portability. All technical drawings, parts lists, and assembly guides are freely available via a GitHub repository, enabling the scientific community to reproduce and enhance the device.</div
Post-Eocene rotations in the Western Alpine realm: a review from sixty eight years of paleomagnetic investigations
No full textInternational audienceA synthesis of more than 55 paleomagnetic studies yielding Tertiary primary or secondary magnetizations is used to evidence the rotations around a vertical axis since 40 Ma in the Western Alps and surrounding areas. In both external and internal zones of the orogenic prism, the rotations seem to be latitude dependent. In particular a widespread Eocene remagnetization of the Mesozoic European cover from Jura to Provence suggests possible effects of small local rotations of the External units of the belt. The most prominent feature is a consistent large (20–60 degrees) counterclockwise rotation observed in internal units and in the Northern Apennine areas. Also, the Corsica- North Sardinia block rotates similarly. Since the late Oligocene, apparent rotations around vertical axis are small North of the Po plain. It implies that the Torino-Monferrato North verging thrust plays a major role in accommodating the differential rotation. Therefore, domains separated from Europe by oceanic sutures ( i.e. Liguria + Corsica − North Sardinia) can play as rigid bodies, while on the contrary, internal deformation deduced from paleomagnetic studies evidence that Apulia cannot be anymore regarded as a rigid body. In the Western Alps, the plate boundary, first localised at the ophiolite suture is then shifted along the Penninic Frontal Thrust. Tectonic models of the Alps that do not take into account the observed rotations have clearly to be reappraised.Une synthèse de plus de 55 études paléomagnétiques basées sur des aimantations primaires ou secondaires d’âge Tertiaire est utilisée pour mettre en évidence les rotations autour d’un axe vertical depuis 40 Ma dans les Alpes occidentales et les régions environnantes. Dans les zones externes et internes du prisme orogénique, les rotations semblent dépendre de la latitude. En particulier, les directions issues d’une ré-aimantation générale à l’éocène de la couverture européenne mésozoïque, du Jura à la Provence, suggèrent des effets possibles de petites rotations locales des unités externes sont mises en évidence. La caractéristique majeure est une rotation anti-horaire importante (20–60 degrés) observée dans les unités internes et dans les zones de l’Apennin septentrional. Le bloc Corse − Nord Sardaigne subit également une rotation similaire. Depuis la fin de l’Oligocène, les rotations apparentes autour de l’axe vertical sont faibles au nord de la plaine du Pô. Cela implique que le chevauchement nord Torino-Monferrato joue un rôle majeur dans la prise en compte de la rotation différentielle. Par conséquent, les domaines séparés de l’Europe par des sutures océaniques (c’est-à-dire la Ligurie + la Corse-Sardaigne) peuvent jouer le rôle de corps rigides, alors qu’au contraire, la déformation interne déduite des études paléomagnétiques montre que l’Apulie ne peut plus être considérées comme un corps rigide. Dans les Alpes occidentales, la limite des plaques, d’abord localisée au niveau de la suture ophiolitique, est ensuite déplacée le long du Chevauchement Pennique Frontal. Les modèles tectoniques des Alpes qui ne prennent pas en compte les rotations observées doivent clairement être réévalués